The great importance offered by the present use of bronchodilators in certain dyspneic respiratory diseases such as asthma, chronic bronchitis and emphysema is known.
Beta-2-mimetics hold an important place among bronchodilators.
In 1948 ALQUIST discovered the existence of receptors that react differently to catecholamines; he described alpha receptors, vectors of exciting reactions and beta receptors, receptors of inhibiting reactions.
In 1967 LANDS differentiated these receptors into beta 1 and beta 2, the beta 1's serving for stimulation of the heart and fatty tissues, the beta 2's serving for relaxing of the bronchial vascular and uterine smooth muscles.
Following this discovery, selective beta 2 medicines (therefore specific of receptors of the same name) were put on the market and their main use was for treatment of asthma.
The bronchodilating activity of the products was shown by the improvement of the forced expiratory volume in 1 second (FEV.sub.1) recorded by spirography.
The clinical activity and use of beta-2-mimetics are well known.
Beta-2-mimetics now exist in various galenical forms permitting their administration:
orally: syrups and tables,
by injection,
by dosing aerosols.
Beta-2-mimetics are active orally but their effects appear only about two hours after their administration. Further, they are inactivated in the digestive tract and by the liver.
The effects are observed more rapidly by injection (subcutaneous or intravenous).
Use in the form of aerosols in undoubtedly the best, provided that the air passages are not congested and the use of the dosing aerosol by the patient is as perfect as possible. Now, few patients correctly use the apparatus made available to them, which frequently ends in abuse of the medicine, because the patient increases the dose, having the impression that one or two puffs are ineffective. Moreover, it is not certain that an aerosol puff reaches the peripheral passages. As already stressed in the case of patients having an active attack of asthmatic disease with bronchial obstruction (aggravated by an infection or by bronchial hypersecretion), it is risky to expect beneficial effects from this aerosol.